Ink compositions, especially those for use with ink jet printers, must satisfy a number of conditions in order to achieve acceptable printing.
The ink composition should possess properties which permit it to be jetted appropriately from an ink jet printer. In ink jet printing, droplets of ink are expelled from nozzles onto a recording medium. The ink should form a meniscus at each nozzle prior to being expelled in the form of a droplet. After a droplet is expelled, additional ink surges to the nozzle to reform the meniscus. Important properties of the ink in this context include the ink's viscosity and surface tension.
Generally, adjustment of the viscosity of an ink composition can negatively affect the print quality and/or drying time of the ink. This may result in excessive feathering or wicking along the paper fibers due to capillary action, and longer drying times at higher viscosity. Adjustments to the surface tension to improve a certain characteristic of the ink may adversely affect other characteristics thereof.
In many applications, fast drying inks are desired. The drying time of an image can limit both the speed and the architecture of an ink jet printer. Faster drying inks allow one to design a faster printer which would not constrain its architecture. However, the drying time of the ink should not be such that it dries in the nozzle of the ink jet printer, thus clogging the nozzle. On the other hand, slow drying inks have limited use in printers requiring high throughput.
Printing different colored inks next to each other often results in intercolor bleeding with conventional inks. Thus, it would be desirable if inks could be formulated which dried instantaneously to minimize intercolor bleeding. Accordingly, fast drying inks are desirable, especially in conjunction with color ink jet printers.
Drying time and print quality of an ink may be affected by the material on which the ink is applied. For example, paper is often sized with sizing components for the purpose of retarding or preventing penetration of liquids into the structure. This is commonly done by introducing a material to the pulp during the paper making operation. Paper may be sized internally or on the surface. Acid sizing chemicals, such as Mon size available from Monsanto Chemical Company, or alkaline sizing chemicals, such as Hercon-76 available from Hercules Company, are precipi-tated onto the fibers primarily for the purpose of controlling penetration of liquids into the final dry paper. This process is known as internal sizing. Surface sizing involves the application of dispersions of film-forming substances such as converted starches, gums and modified polymers to previously formed paper. Surface sizing imparts strength to the paper and thus high quality printing papers are often surface sized as well. These and other materials tend to adversely affect the manner in which a particular ink dries.
As used herein, the term "plain paper" represents all standard office and xerographic paper except for photographic and thermal paper.
Tomida et al U.S. Pat. No. 4,838,938 discloses a recording liquid comprising a special host molecule with inclusion ability, a dye, a liquid medium, a dispersing agent, a surfactant, a viscosity controller, and a surface tension controller. The liquid medium may comprise water and/or organic solvent. Organic, solvents include isopropyl alcohol and 1-methyl-2-pyrrolidone. The surfactant may comprise cationic, anionic or nonionic surfactant. The viscosity controller may comprise polyvinyl alcohol, celluloses, water soluble resins, etc. The surface tension controller may comprise diethanolamine, triethanolamines, etc. A preferred viscosity at 25.degree. C. is 5 centipoise or less, more preferably 3 centipoise or less, with a surface tension of 35 to 65 dynes/cm.
Koike et al U.S. Pat. No. 4,923,515 discloses an ink composition comprising water, an organic solvent, a dye, surfactants, viscosity controllers, and surface tension controllers. The organic solvents may comprise alkyl alcohols, amides, ketones or ketoalcohols, ethers, alkylene glycols, etc.
Schick et al U.S. Pat. No. 4,847,316 discloses an ink composition comprising a homogeneous blend of water dispersible polyurethane, water dispersible polyester, a solvent system containing water or water admixed with a cosolvent. The cosolvent may include diethylene glycol monomethyl ether, diethylene glycol, n-propyl alcohol, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, and diethylene glycol monobutyl ether. Water comprises at least about 90.0 weight percent of the solvent system.
Hayes U.S. Pat. No. 4,150,997 discloses an ink composition comprising an aqueous solution, a dye solubilizer, and butyl carbitol. The percentage by weight of butyl carbitol may be from about 5 to 7 percent. The butyl carbitol acts as a dye stabilizer and wetting agent.
Carumpalos et al U.S. Pat. No. 4,163,001 discloses an ink composition comprising a laked alkali stable basic dye wherein the laking agent is dispersed in a liquid medium having butyl carbitol, water, a nonionic surfactant, and an amino alcohol.
Cross et al U.S. Pat. No. 4,378,564 discloses an ink composition comprising water, dye, and glycol ether. The glycol ether may include butyl cellosolve (glycol monobutyl ether), butyl carbitol, and mixtures thereof.
Fugii et al U.S. Pat. No. 4,508,570 discloses an aqueous ink component comprising a water-soluble dye, a polyhydric alcohol and/or an alkyl ether, water, and at least one water-soluble non-ionic surface active agent. The non-ionic surface active agent may comprise a polyoxyethylene alkyl amine, a polyoxyethylene alkyl phenyl ether or a polyoxyethylene alkyl ether.
Okuzono et al U.S. Pat. No. 4,740,549 discloses a wipe-erasable ink composition for a writing board, and is thus irrelevant to ink jet inks. The ink composition comprises a dye, an organic solvent, and a non-ionic surface active agent. The nonionic surface active agent may include polyoxyethylene sorbitol monostearate, polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, etc.
U.S. Pat. No. 4,889,877 to Seitz discloses a printing ink composition comprising water, a non-volatile diluent, oil-containing microcapsules, a protective colloid blend, and a binder emulsion or alkali soluble resin. The non-volatile diluent may comprise methyl glucoside, dimethyl urea, sorbitol, erythritol, and polyoxyethylene polyols.
U.S. Pat. No. 4,836,852 to Knirsch et al. discloses an ink composition comprising a dye in a mixture of water and glycol wetting agents. The dye may include solubilizing agents such as N-methyl pyrrolidone and derivatives thereof. A surface tension of between 35 and 40 dynes/cm is disclosed.
Although the ink compositions of the prior art provide inks with certain advantageous qualities, it is desirable to provide inks having fast drying times and good print quality.